The present invention relates to applications where valve-type devices are utilized to control the flow of a substance to be very carefully measured and where it is desirable to completely remove all of the substance from the valve between filling cycles.
In some instances, valves of this type are utilized in food processing and container filling arrangements where it is highly desirable to obtain an accurate cut-off in metering such materials.
Also, in many applications, particularly food metering operations, it is important that a metering valve arrangement provide a means to clear all material off the surfaces of the valve members contacting the material to prevent cross contamination and bacteriological growth within the substance being metered by completely removing all sources for such growth with each cycle of the metering valve.
In applications where metering valves are utilized in food processing or in the processing of other materials for human consumption, local, state and federal regulatory restrictions and the continuing strengthening and increasing scope of the restrictions necessitate the use of easily cleaned mechanical devices since many regulations impose severe restrictions on the handling of food and other materials for human consumption by human hands or the handling of such materials in open atmosphere.
Heretofore, various valve arrangements have been provided for metering the flow of various materials into containers where the valves have been of the arrangements generally known in the art, primarily, gate-type valves and ball valves.
Such valves have operated satisfactorily in many applications where the material to be metered is of relatively low viscosity.In such applications, the valve adequately meters the material and because of the low viscosity of the material, the clean-off of the valve is of little concern because the material drains from the valve.
However, in applications where such valves have been utilized in filling food containers with materials, such as mashed potatoes, applesauce or other highly viscous food products, such valves are not satisfactory because the material which clings to the valve after closure first adversely affects the weight of the material introduced into the container and secondly provides a site for the growth of bacteria.
Moreover, such prior art arrangements provided no means for post-operation valve cleanoff which would eliminate such problems.
In some applications where valves are utilized to meter the flow of food or other viscous material, arrangments are known where a wiper mechanism has been provided to wipe off the surface of the valve after closure. In such applications, the wiper mechanism has not been entirely satisfactory because the wiper is a mechanical device which first of all abrades and ultimately adversely affects the valve member itself, and secondly because of the mechanical nature of the wiper configuration, maintenance is from time to time required.
Additiionally, such wiper-type valves are generally complex in fabrication and expensive and even in simplest design do not adequately clean the valve of all substances between valve cycles.